detachments of workmen being
first marched to the depots and supplied with all the necessary tools
for carrying on the work, now commence their labors under the protection
of these guards. By daybreak the construction of the first parallel, and
the trenches connecting it with the depots, will be sufficiently
advanced to cover the men from the fire of the place; the guards will
therefore be withdrawn, and the workmen continue their labors during the
day to give the trenches the proper size and form.

The _parallels_ are the long lines of trench which envelop the besieged
work, and serve both as covered ways for the circulation of the
besiegers, and as means of defence against sorties from the garrison;
they are therefore arranged with banquettes for musketry fire. The
boyaux are trenches run in a zigzag direction along the capitals of the
front of attack, and are intended exclusively for the circulation of the
troops; they have no banquettes. The first parallel is about six hundred
yards from the place, and consequently beyond the reach of grape. It is
constructed by the _simple sap_. After the first night, the guards,
instead of advancing in front of the work, are placed in the trenches.

The second parallel (B) is made some three hundred or three hundred and
fifty yards from the place, and being much exposed to grape, the
_flying-sap_ is employed in its construction. Batteries (H) are
established between the first and second parallels to silence the fire
of the demi-lunes of the collateral bastions, and others (I) near the
second parallel, to enfilade the faces of the front of attack. These are
armed in part with mortars and in part with heavy siege-pieces.

The works are now gradually pushed forward to the third parallel, (C),
which is constructed about sixty yards from the salients of the place.
As the operations of the besiegers are here greatly exposed to musketry
fire, the trenches are constructed by the _full-sap_. The third
parallel, having to contain the guards of the trenches, and being of
less development than the two preceding, is made much wider. The second
parallel now contains the reserve, and the first parallel becomes the
depot of materials. _Demi-parallels_ (G) are frequently established
between the second and third, to be occupied by detachments of guards.

The operations of defence during this period are so directed as to
harass the workmen in the trenches and retard the advance of the works
of at